Recent variation in reach‐scale bankfull discharge in the Lower Yellow River

Abstract

Bankfull discharge is a key parameter in the context of river engineering and geomorphology, as an indicator of flood discharge capacity in alluvial rivers, and varying in response to the incoming flow and sediment regimes. Bankfull channel dimensions have significantly adjusted along the Lower Yellow River (LYR) due to recent channel degradation, caused by the operation of the Xiaolangdi Reservoir, which has led to longitudinal variability in cross‐sectional bankfull discharges. Therefore, it is more representative to describe the flood discharge capacity of the LYR, using the concept of reach‐averaged bankfull discharge. Previous simple mean methods to estimate reach‐scale bankfull discharge cannot meet the condition of flow continuity or account for the effect of different spacing between two sections. In this study, a general method to calculate cross‐sectional bankfull discharge using the simulated stage‐discharge relation is outlined briefly, and an integrated method is then proposed for estimating reach‐scale bankfull discharge. The proposed method integrates a geometric mean based on the log‐transformation with a weighted average based on the spacing between two consecutive sections, which avoids the shortcomings of previous methods. The post‐flood reach‐scale bankfull discharges in three different channel‐pattern reaches of the LYR were estimated annually during the period from 1999 to 2010 using the proposed method, based on surveyed post‐flood profiles at 91 sedimentation sections and the measured hydrological data at seven hydrometric sections. The calculated results indicate that: (i) the estimated reach‐scale bankfull discharges can effectively represent the flood discharge capacity of different reaches, with their ranges of variation being less than those of typical cross‐sectional bankfull discharges; and (ii) the magnitude of the reach‐scale bankfull discharge in each reach can respond well to the accumulative effect of incoming flow and sediment conditions. Finally, empirical relationships for different reaches in the LYR were developed between the reach‐scale bankfull discharge and the previous four‐year average discharge and incoming sediment coefficient during flood seasons, with relatively high correlation coefficients between them being obtained, and the reach‐scale bankfull discharges in different reaches predicted by the delayed response model were also presented for a comparison. These relations for the prediction of reach‐scale bankfull discharges were validated using the cross‐sectional profiles and hydrological data measured in 2011. Copyright © 2013 John Wiley & Sons, Ltd.

Effect of human‐controlled hydrological regime on the source, transport, and flux of particulate organic carbon from the lower Huanghe (Yellow River)

“…This figure is available in colour online at wileyonlinelibrary.com/journal/espl 12.65 km 3 ) began operation, the flows and sediments entering the lower Huanghe have been totally altered. The accumulated sediment eroded from the lower Huanghe channel is estimated up to c. 1.36 km 3 (average~100 Mt a À1 ) in 1999 À 2010 (Xia et al, 2014b), which accounts for about 60% of the fluvial sediment flux to the sea during this period. On the other hand, the majority of sediment (about 80%) from the middle reaches is now trapped in the Xiaolangdi Reservoir.…”

“…Consequently, the lower Huanghe riverbed is being scoured by the clear water flow with low SSC released from the reservoir (Yu et al, 2013a). The accumulated sediment eroded from the lower Huanghe channel is estimated up to c. 1.36 km 3 (average~100 Mt a À1 ) in 1999 À 2010 (Xia et al, 2014b), which accounts for about 60% of the fluvial sediment flux to the sea during this period. As a result of continuous scouring in the lower Huanghe, the median grain size of the riverbed material gradually increased from 36~56 μm in 1999 to about 151 μm in 2012 (Xia et al, 2014a).…”

Monitoring Riverbank Erosion in Mountain Catchments Using Terrestrial Laser Scanning

“…Among the aforementioned sediment sources, riverbank erosion is considered a rather significant process in the context of fluvial dynamics as it involves a considerable fraction of the total sediment yield being supplied by riverbanks although its contribution varies between rivers [12][13][14][15]. Riverbank erosion may be caused by different phenomena, occurring with differing magnitudes and frequencies [16,17].…”

Relationships between Soil Nutrients and Plant Diversity in Riparian Woodlands Along the Middle and Lower Reaches of the Yellow River, China

“…The 168 km river section covers the transition zone between the middle and lower reaches of the Yellow River in Henan Province, China (Figs 1a and 1b). The lower Yellow River is affected by heavy sediment deposition, forming a typical wandering "perched river" with its river bed higher than the ground elevation outside banks and a large riparian zone, which is well-restricted by and bordered with the left and right levees, and the total width extends from 5 to 20 km [36]. Field sampling was conducted within the levees on both sides of the river.…”

“…In recent years there has been a decrease in the number of total days of rain, but a subsequent increase in the frequency of heavy rainfall events [25]. The channel slope of the Yellow River in the study area ranges from 0.1 to 0.5‰ [36]. The gentle channel slope leads to a unique continuous transition landscape of hills-plain, providing a broad floodplain suitable for cultivation.…”